For many years, validation stickers have been applied to motor vehicles to indicate that applicable taxes have been paid and/or required registrations and inspections have been completed. In a common application, small stickers (typically on the order of about 2.5 by 3.8 centimeters or so (1 by 1.5 inches) and sometimes colloquially referred to as "tabs") are applied to a designated location on the vehicle's license plate(s) to indicate that annual licensing taxes and registration fees have been paid. Other illustrative examples include application of stickers as proof of satisfactory vehicle safety inspections, satisfactory vehicle emission control inspections, and insurance coverage. In many instances, stickers are stacked, i.e., each year the new sticker is applied directly over the sticker from the previous year.
One effect of increased tax rates, stricter insurance requirements, more rigorous environmental and other regulatory requirements, etc., is that possession of validation stickers may represent substantial economic value. As a result, validation stickers have increasingly become targets for theft. In order to avoid paying applicable taxes, or to obtain proof of inspection for vehicles that could not meet applicable requirements, etc., thieves may remove stickers from the license plates of vehicles where the stickers have been legitimately applied and seek to illegally reapply them to the license plates of other vehicles. Removal of stickers is typically easier when the sticker is applied to a portion of a larger flat surface and when the sticker is of a highly cohesive, strong construction. Stickers which are stacked may be particularly susceptible to theft because the stack provides a number of interfaces where delamination, or layers in which cohesive failure, may be induced, e.g., with a razor blade, utility knife, scalpel, etc. Also, underlying stacked stickers tend to reinforce the topmost current sticker, thereby making it easier to remove and handle without apparent damage.
In order to avoid stacking of stickers, states or provinces may issue stickers with less aggressive adhesive and higher tear strength to facilitate their removal at the time the following year's sticker is applied. Such increased ease of removability, however, also facilitates unauthorized removal of stickers for improper application to other vehicles. Another alternative to stacking stickers is to provide a series of designated locations on a license plate for stickers to be applied, typically in prescribed sequence. Many states or provinces do not wish to use license plates with such multiple locations, however, because the resultant license plates become unsightly, it is harder to readily determine if current stickers are presented, there is greater probability of incorrect application of a sticker, and available space on the face of the license plate may be desired for other features, e.g., state mottos, vehicle classification information, aesthetic presentation, etc.
To date, certain steps have been taken to inhibit unauthorized removal and theft of intact validation stickers, including use of very strong adhesives, stickers with low tear strength, and perforated stickers. Despite these steps, however, additional and improved alternatives for inhibiting removal of stickers are desired.